The present invention relates to a brake that exerts a braking force to a revolving portion of a hydraulic motor.
In recent years, a hydraulic motor is used for driving a construction machine such as an asphalt finisher and the like. In the case where a hydraulic motor is mounted on a construction machine, the machine should be equipped with a parking brake that exerts a braking force to the hydraulic motor while the supply of a driving fluid to the construction machine is suspended.
A typical brake of this kind includes one or more fixed friction discs connected to a fixed portion of the hydraulic motor so as to move in the direction of the axis, one or more rotating friction discs connected to the revolving portion of the hydraulic motor so as to move in the direction of the axis and to rotate as a single unit, a spring for exerting a pressing force to the fixed friction discs and the rotating friction discs to bring these friction discs into frictional contact with respect to each other, a releasing piston provided between the spring and the fixed friction discs and the rotating friction discs for transmitting a pressing force exerted by the spring when it moves closer to the fixed friction discs and the rotating friction disc by being pressed by the spring, and a releasing passage for moving the releasing piston away from the fixed friction discs and the rotating friction discs to release the fixed friction disc and the rotating friction discs from frictional contact with respect to each other.
Since the construction machine as described above is a motor vehicle that is driven on the public road, it is required to be equipped with a brake such as a disc brake or a drum brake, which exerts a braking force to the vehicle as needed in addition to a parking brake as described above according to the safety standard for the road transportation vehicles.
In the construction machines, since it is required to provide a brake that exerts a braking force as needed in addition to a parking brake, there is recognized disadvantages in that the braking system is forced to be upsized as a whole and that the cost is increased.
Accordingly, it is an object of the present invention to provide a brake for a hydraulic motor, which is smaller in size, lower in price, and higher in the level of safety.
This object may be achieved by providing a brake for a hydraulic motor disposed between the fixed portion of a hydraulic motor and the rotating portion of the hydraulic motor that rotates when a driving fluid is fed thereto for braking the rotating portion, wherein the rotating portion is braked when the supply of the driving fluid is being suspended and released when the supply of driving fluid is being supplied, which brake comprising: one or more fixed friction discs connected to the fixed portion so as to move in the direction of the axis, one or more rotating friction discs connected to the rotating portion so as to move in the direction of the axis and to rotate as a single unit, a spring for exerting a pressing force to the fixed friction disc and the rotating friction discs to bring these friction discs into frictional contact with respect to each other, a releasing piston disposed between the spring and the fixed friction discs and said rotating friction discs for transmitting a pressing force exerted by the spring to these friction discs when it moves closer to the fixed friction discs and the rotating friction discs by being pressed by the spring, a releasing passage for moving the releasing piston away from the fixed friction disc and the rotating friction discs by leading the driving fluid being fed to the hydraulic motor to the releasing piston to release the fixed friction disc and the rotating friction discs from frictional contact with respect to each other, a braking piston supported on the fixed portion so as to move in the direction of the axis, and a braking passage for pressing the braking piston against the fixed friction discs and the rotating friction discs by leading a high pressure fluid to the braking piston to bring these fixed friction discs and rotating friction discs into frictional contact with respect to each other.
When a driving fluid is fed to the hydraulic motor, the rotating portion of the hydraulic motor rotates, and at the same time, the driving fluid is conducted to the releasing piston as well through the releasing passage, so that the releasing piston moves against the pressing force exerted by the spring away from the fixed friction discs and the rotating friction discs to release the fixed friction discs and the rotating friction discs from frictional contact with respect to each other.
Thus, in order to brake the rotating hydraulic motor as needed, a high pressure fluid is led through the braking passage to the braking piston, and the braking piston is moved axially to the fixed friction discs and the rotating friction discs. When the braking piston is pressed against the fixed friction discs and the rotating friction discs, these fixed friction discs and the rotating friction discs is brought into frictional contact with respect to each other so that the rotating portion of the hydraulic motor is braked. Therefore, only by adding a braking piston and a braking passage, a braking force may be exerted to the hydraulic motor any time, and thus a downsized brake with higher safety may be realized at a low cost.
When the supply of a driving fluid to the above-described hydraulic motor is suspended, the rotating portion stops rotating. At that time, since the supply of driving fluid to the releasing piston is also suspended, the releasing piston is moved closer to the fixed friction discs and the rotating friction discs by being pressed by the spring to transmit the pressing force of the spring to the fixed friction discs and the rotating friction discs. Consequently, the fixed friction discs and the rotating friction discs are brought into frictional contact with respect to each other to brake the rotating portion of the hydraulic motor.
By constituting a brake as described in the second aspect of the present invention, the releasing piston and the braking piston are radially overlapped so that the axial length of the brake may be shortened.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 11-193952 (filed on Jul. 8, 1999), which is expressly incorporated herein by reference in its entirety.